Bumblebees – canaries in the countryside?

A headline in the UK’s The Guardian this week, stated that “Bumblebees’ decline points to mass extinction“. It was triggered by a report in the journal Science, titled ‘Climate change contributes to widespread declines among bumblebees across continents’. This report analysed long-term data for 66 bumblebee species across both North America and Europe which concluded that “increasing frequencies of temperatures that exceed historically observed tolerances help explain widespread bumblebee species decline” and that the likelihood of a bumblebee population surviving in any given place has declined by 30% in the course of a single human generation. The researchers say the rates of decline appear to be “consistent with a mass extinction”. Drawing the conclusion that ‘decline’ points to ‘mass extinction’ (defined as “a widespread and rapid decrease in the biodiversity on Earth”) may seem a stretch, but let’s unpick all of this and see where it get us (and let’s see if the canaries in the post title feature at all)….

Bumblebees There around 20,000 species of bee on this planet. Of those around 250 are bumblebees (and just one is the well-known Honey bee Apis mellifera). Here in the UK we have 24 bumblebee species (25 if you include the reintroduced Short-haired Bumblebee). Current thinking is that our bumblebees are in decline because of habitat loss, mainly through intensive agriculture and loss of wildflower meadows. Two species have been driven to extinction here since 1940 (Cullum’s bumblebee Bombus cullumanus was last seen on the Berkshire Downs in 1941, and (before it’s reintroduction) the Short-haired bumblebee Bombus subterraneus was last seen at Dungeness on the Kent coast in 1988 and officially declared extinct in 2000). A third of our remaining species are currently listed on at least one of the English, Welsh and Scottish conservation priority species lists due to large-scale declines in their distribution. Which can’t be good, can it? Now, while we here at The War on Wildlife Project think that all wildlife matters, and that existence shouldn’t ever be measured in terms of ‘usefulness to humans’, let’s ask the question anyway: bumblebees are quite pretty, they don’t sting, but does it really matter if they’re in decline? It most certainly does, and this is where the ‘canary in the coal mine’ metaphor comes in. Firstly, though, purely from an economic standpoint, according to the independent International Union for the Conservation of Nature (IUCN) pollinators provide an ecological service that is necessary for the reproduction of nearly 75 percent of the world’s flowering plants, including more than two-thirds of the world’s crop species. Bumblebees are among the most important plant pollinators, and they are the exclusive insect pollinator of greenhouse tomatoes. Bumblebees also help pollinate many wildflowers, allowing them to produce seeds. If no seeds are produced, widlflowers – often the basis of complex food chains – will disappear, resulting in declines in both the abundance and distribution of a range of other species from other insects to mammals and birds. Which brings us to canaries (which are birds of course, but otherwise unrelated to bumblebees). However…

Sentinel species Canaries are finches, small songbirds that during the 18th and 19th centuries were caged in huge numbers because bringing them into our dark and dismal homes and hearing them sing made us feel better. It didn’t do much for the birds of course, and they were treated pretty much as replaceable items with a short shelf life. How did they end up being used in coal mines though? All songbirds are adapted to using huge amounts of oxygen to power their flight muscles (the large ‘breast muscles’ birds use to fly). Combined with their small size, a naturally high metabolic rate, and rapid uptake of large volumes of air, birds are far more sensitive to airborne poisons than we are – and there are a lot of poisons in the air in coal mines: particularly methane and carbon monoxide (the former trapped in coal seams as they form, the latter by the oxidation of coal). Trapped in small cages and carried down into the totally unfamiliar environment of a coalmine it’s a wonder that canaries weren’t dying in vast numbers anyway, but they rapidly passed out when the miners reached a pocket of gas. That gave the miners time to escape (and hopefully revive the canary before it died). While (thankfully) the practice of using animals as living gas detectors has ended, a legacy has been the concept of ‘sentinel species’ – species that warn us humans of threats or danger. If we stop to think about it though (and we here at The War on Wildlife Project think about this quite a lot) all declining species are ‘sentinel species’. Every population decline – from the smallest algae to the largest mammal and bird – is a sign that something in the environment has changed. And while change over the long-term is normal (and is what drives evolution through natural selection of course), any report that suggests that declines in the population of so many bumblebee species across such huge areas has occurred in less than a hundred years – caused, again according to the IUCN, ‘by a variety of threats that range from habitat loss and degradation to introduced diseases and pesticide use‘ – should cause us huge concern.

Does mass extinction include us? That this particular report now adds climate change to the mix of threats facing bumblebees should be even more concerning. Particularly as it follows an extremely clear warning from UN Secretary-General Antonio Guterres at the World Economic Forum in Davos last month: “We will be destroyed by climate change, not the planet. This will be for us a clear indication that we absolutely need to change course…Humankind has declared a war on nature and nature is striking back in a very violent way“. ‘Declared a war on nature‘ ? Yes, we might have said something like that in the past ourselves… The Secretary-General is absolutely correct of course. The planet will survive. Our future is far less certain. But if we think about our future just in terms of bumblebee loss, it’s clear that we’re being very casual about our long-term survival. We’ve made huge changes across the planet (largely because we want the land for food production), we’re using chemical warfare on the planet’s invertebrates (largely because we won’t share our food with anything else), we’ve introduced species and diseases (largely because we want to eradicate native wildlife or refuse to recognise that trade is not the only thing that matters), and now we’re adding climate change to the threats that biodiversity – and by extension us – are facing (change driven largely by – well, virtually everything about the way we live our lives).

Does it matter if we lose bumblebees? It matters because all life matters, but if that isn’t a persuasive enough argument then how about we understand the fact that they are a ‘sentinel species’, telling us that we are making the planet unfit and unhealthy – and that is as bad for bumblebees and canaries as it is for us.